This Week's Night Sky: A Lunar Eclipse and Mars Meets a Lion

As summer reaches its official end, Venus puts on a show and a blood moon appears.

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In this simulated view, Mars appears in front of the constellation Leo. The pair will appear together in Earth skies this week.

Skychart by A. Fazekas, Skysafari

PUBLISHED September 21, 2015

Venus most brilliant. Look toward the low southeast sky at dawn in mid-September and your eye can't help but be drawn to a sparkling point of light known as the “morning star.”

That “star” is the second planet from the sun, Venus, shining about 17 times brighter than Jupiter, the other major planet visible in morning skies this month. And on Monday, September 21, Venus puts on its best morning show for the entire year, reaching magnitude 4.8, the brightest it can get in our skies.

Through a small telescope, the planet's disk will look like a miniature version of the crescent moon, thanks to the geometry of our two worlds in relation to the sun. You don't want to miss this show because Venus won't appear this bright and high in the sky again until 2016.

Autumn equinox. At 4:21 a.m. on Wednesday, September 23, the fall season kicks off in the Northern Hemisphere and spring starts in the Southern Hemisphere.

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Mars is in close conjunction with Regulus, the brightest star in the constellation, Leo.

Skychart by A. Fazekas, SkySafari

The September equinox marks one of the four major turning points in the seasonal cycle. Seasons occur on Earth because the planet’s axis is tilted at 23.5 degrees with respect to its orbital plane. During the fall and spring equinox, that axis is tilted neither away nor towards the sun but has both Northern and Southern hemispheres experiencing equal amounts of sunshine.

The word equinox comes from Latin meaning “equal night” and refers to the approximately 12-hour-long day and night that occurs only on these two days of the year, with the sun rising due east and setting due west.

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This simulation shows the view from the moon of a backlit Earth during the deepest part of a total lunar eclipse. The red ring is caused by sunlight traveling through Earth’s hazy atmosphere.

Illustration by NASA's Scientific Visualization Studio

Mars walks with Leo. Early risers on Thursday, September 24, should look toward the low western horizon to catch sight of Mars meeting up with Regulus, the brightest star in the constellation Leo, the lion. The cosmic duo will be separated by less than 1 degree, which is less than the width of your index finger held at arm’s length. Bracketing the dim pair will be the super-bright planets Venus, above, and Jupiter, below.

Super moon shadow. The moon will appear to blush orange-red late Sunday night/early Monday morning as it undergoes a total eclipse, visible across both American continents and Europe. This lunar eclipse is the last in a series called a tetrad, in which four of these rare events occur, each separated by about six months.

Earth's shadow will begin to take a bite out of the moon's silvery disk at 9:07 p.m. EDT. The lunar eclipse then enters totality at 10:11 p.m. EDT and will remain there for 72 minutes. The moon’s reddish appearance gives this type of eclipse the nickname of “blood moon.”